Bismuth ladder polymers: Structural and thermal studies of [Bi(OCH2CH2)3N]n and [(BixTb1-x(O2C2H2) 3N·2H2O]n

Article abstract of DOI:10.1016/S0020-1693(02)01381-6

[Bi(OCH₂CH₂)₃N],(Bi(TEA)), may be prepared by reaction of in situ generated Bi(OH)₃ with triethanolamine in refluxing methanol. The complex crystallizes from solution as a double ladder polymer via the formation of additional metal-oxygen dative bonds to yield hypercoordinate and hypervalent metal centers. The structure of Bi(TEA) is very similar to that of Bi(O₂CCH₃)₃N. The heterobimetallic nitriloacetate complex containing Bi and Tb was prepared by reaction of (NH₄)₃[Bi(Nta)₂] with terbium nitrate in aqueous solution. Heating samples of [Bi(OCH₂CH₂)₃N]_n to 1000°C results in the formation of Bi₂O₃. It was shown that thermolysis of the [(Bi_xTb_1-x(O₂C₂H₂) ₃N)·H₂O]_n occurs in two stages, viz. the deaquation and pyrolysis of the ligand.

Full text of DOI:10.1016/S0020-1693(02)01381-6

Inorganica Chimica Acta 346 (2003) 249ꢁ255
/
www.elsevier.com/locate/ica
Note
Bismuth ladder polymers: structural and thermal studies of
[Bi(OCH2CH2)3N]n and [(BixTb1ꢀx(O2C2H2)3N×2H2O]n
/
Robert E. Bachman a,1, Kenton H. Whitmire a,*, John H. Thurston a, Aurelian Gulea b,
Olexa Stavila b, Vitalie Stavila b
a Department of Chemistry, Rice University, P.O. Box 1892, Houston, TX 7251-1892, USA
b Department of Chemistry, State University of Moldova, Chisinau, Moldova
Received 29 April 2002; accepted 25 September 2002
Abstract
[Bi(OCH2CH2)3N],(Bi(TEA)), may be prepared by reaction of in situ generated Bi(OH)3 with triethanolamine in refluxing
methanol. The complex crystallizes from solution as a double ladder polymer via the formation of additional metalÃ
/oxygen dative
bonds to yield hypercoordinate and hypervalent metal centers. The structure of Bi(TEA) is very similar to that of Bi(O2CCH3)3N.
The heterobimetallic nitriloacetate complex containing Bi and Tb was prepared by reaction of (NH4)3[Bi(Nta)2] with terbium nitrate
in aqueous solution. Heating samples of [Bi(OCH2CH2)3N]n to 1000 8C results in the formation of Bi2O3. It was shown that
thermolysis of the [(Bix Tb1ꢀx (O2C2H2)3N)×
/
H2O]n occurs in two stages, viz. the deaquation and pyrolysis of the ligand.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Bismuth ladder polymer; MetalÃoxygen dative bond; Nitriloacetate complexes
/
1. Introduction
which often leads to extensive oligomerization and/or
extreme water sensitivity. In an effort to control both
the hydrolytic stability and the degree of oligomeriza-
tion (and hence the volatility), we have examined the
properties of the bismuth complex of the chelating
ligand triethanolamine, [Bi(OCH2CH2)3N]n (1), or ‘bis-
matrane’ [5]. It was hoped that the multidentate binding
of the oxygen ligand would impart a degree of hydro-
lytic stability while the presence of an additional
intramolucular Lewis base, in the form of the nitrogen
atom, would help prevent oligomerization. While the
former goal was achieved, the latter was not, as
bismatrane aggregates in the solid state to form a
double-ladder polymer.
Bismuth alkoxides have attracted attention as pre-
cursors to oxide materials with a wide variety of
properties [1]. For example, bismuth-containing oxide
materials have been shown to be catalysts for oxidation/
ammoxidation [2], high temperature superconductors
[3], ionic conductors [4], and piezoelectrics [1c,3b]. In a
general sense there are two routes to such materials:
CVD or solꢁgel processing. For CVD applications, the
/
alkoxide precursor must be volatile and pyrolize cleanly
so as not to leave unwanted contaminants in the final
oxide. In the solꢁgel case, the alkoxide must be soluble
/
in organic solvents and its hydrolysis should be con-
trollable. Unfortunately, the preparation of bismuth
alkoxide precursor materials is complicated by the Lewis
acidic nature of the bismuth center in these complexes,
In some heterometallic aminopolycarboxylates
1
M1M(LxLy ) the donor atoms of monoamine ligand
(L) occupy only a part of the sites in the metal
coordination sphere and the rest of the sites can be
completed by the donor atoms of additional (L1) ligands
or by the active centers of the adjacent complexes [6].
Availability of the cations M1 in the complexonates and
competition between two different metals (M and M1) in
involving the oxygen atoms of aminopolycarboxylic
ligand (L) into their coordination spheres frequently
* Corresponding authors. Tel.: ꢂ
/
1-713-348 4082; fax: ꢂ1-713-348
/
5155.
E-mail addresses: rbachman@sewanee.edu (R.E. Bachman),
chem@rice.edu (K.H. Whitmire).
1
Present address: Department of Chemistry, University of the
South, Sewanee, TN 37383, USA.
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 3 8 1 - 6

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R.E. Bachman et al. / Inorganica Chimica Acta 346 (2003) 249ꢁ255
/
result in the formation of polymers. Structural studies of
bimetallic aminopolycarboxylates make it possible to
elucidate the role of metal atoms in crystal structure
formation. We have synthesized, for the first time, the
mixed-metal terbium(III) and bismuth(III) nitrilotriace-
tate complex compound of the composition
with arsenazo III as an indicator. Elemental Anal. Calc.
for [(Bi0.7Tb0.3(O2C2H2)3N×2H2O]n: Bi, 35.1(34.74); Tb,
11.5 (11.35); N, 3.09 (3.33); C, 16.80 (17.11); H, 2.80
/
(2.39)%.
2.3. Thermogravimetric analysis of 1
[(BixTb1ꢀx(O2C2H2)3N)×
/
2H2O]n (2). In this paper, we
discuss the unique structures of 1 and 2, as well as the
solid-state transformation of the complexes into bis-
muth-based oxide materials.
Sample 1 (10ꢁ20 mg) was heated to 1000 8C in an
/
argon atmosphere. The material decomposed in two
steps between 303 and 410 8C to yield Bi2O3 (identified
by powder diffraction). The total weight loss for these
two processes was 35.1 versus the theoretical value of
34.4% for the formation of Bi2O3. Repeating the
analysis in an oxygen atmosphere resulted in an initial
weight loss at 293 8C of 40.1% followed by a weight gain
at 748 8C of 5.3%. The overall weight loss of 34.8% is
also in agreement with the formation of Bi2O3.
2. Experimental
2.1. Synthesis of [Bi(O2CH2CH2)3N]n (1) [7]
Bi(NO3)3 (15.2 g) was dissolved in a minimal amount
of dilute nitric acid (Â0.1 M). An aqueous solution of
/
approximately 1 M NaOH was prepared and added to
the Bi(NO3)3 solution with vigorous stirring. The
2.4. Thermogravimetric analysis of 2
yellowꢁ
/
white precipitate that immediately formed was
Sample 2 (100 mg) was heated to 800 8C in an air
atmosphere. Differential thermal analysis of the com-
plex 2 indicated a dehydration step at approximately
collected by filtration and suction dried for several
minutes to yield a damp paste. Without any further
purification, this material was added to a solution
prepared from 4.5 g of sodium in 100 ml of ethanol.
Triethanolamine (15 g) was added and the reaction was
80ꢁ190 8C with an endothermic effect, corresponding to
/
the removal of two water molecules {%H2O (calc.) 8.66;
%H2O (exp.) 8.50}. An exothermic decomposition
process occurs between 220 and 470 8C with the
formation of an inorganic residue.
heated to 65ꢁ70 8C overnight. After being allowed to
/
cool to room temperature (r.t.), charcoal was added and
the mixture was filtered through diatomaceous earth.
The clear filtrate was then diluted with 200 ml of
methanol and allowed to stand for several weeks. The
product slowly crystallized from the reaction mixture as
fine colorless needles. 1H NMR (ppm, D2O): 2.8
(broad), 4.0 (broad).
2.5. Structure of 1
All cell determinations and data collection were
carried out on a Rigaku AFC5S at r.t. The crystals
chosen for examination were mounted on glass fibers
using epoxy cement. As a result of their needle-like
morphology and the internal structure of the material,
many of the crystals examined proved to be twinned.
However, after several unsuccessful trials a suitable
2.2. Synthesis of [(BixTb1ꢀx(O2C2H2)3N)×
(2)
/2H2O]n
To a suspension of 0.433 g (0.001 mol) BiNta×
/2H2O
crystal of approximately 0.1ꢃ
/
0.1ꢃ
0.4 mm3 was found.
/
[12] and 0.191 g (0.001 mol) of H3Nta in water was
added 0.237 g (0.003 mol) of NH4HCO3. The mixture
was heated on a water bath until the complete dissolu-
tion of the precipitate, then a solution of 0.435 g (0.001
The unit cell was determined by the least-squares
refinement of 25 carefully centered reflections well
distributed in reciprocal space. Crystal stability was
monitored by a periodic measurement of three check
reflections. No appreciable decay was measured.
mol) Tb(NO3)3×
/
5H2O in a minimum amount of water
was added. The resulting solution was allowed to stand
overnight to effect crystallization. The product was
recrystallized from water solution. The crystals were
collected by filtration, washed with ethanol and then
dried in air. The compound is stable in air, is poorly
soluble in water, and insoluble in alcohol, ether,
acetonitrile, acetone and tetrahydrofuran. Yield 65%.
The presence of bismuth in the complex was deter-
mined gravimetrically by precipitation of the metal as
BiOCl through reaction of the complex with a sodium
stannate solution. The presence of terbium was con-
The structure was solved by Patterson methods,
which allowed location of the bismuth atoms. The other
nonhydrogen atoms were located in the difference map
during refinement. All nonhydrogen atoms were refined
anisotropically and the hydrogen atoms were included in
calculated positions using a standard riding model.
During the latter stages of refinement one of the
ethylene chains was found to be disordered over two
positions. The remaining essential information related
to both the data collection and the refinement is
provided in Table 1 and the significant bond distances
and angles are included in Table 2.
firmed as the EDTA adduct using UVꢁVis spectroscopy
/

R.E. Bachman et al. / Inorganica Chimica Acta 346 (2003) 249ꢁ
/255
251
Table 1
Crystallographic data for 1 and 2
Table 2
˚
Key bond lengths (A) and angles (8) for 1
Empirical formula
Formula weight
C6H12BiNO3
355.15
C6H10Bi0.68NO8Tb0.32
415.83
Bond lengths
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(2)Ã
Bi(2)Ã
Bi(2)Ã
Bi(2)Ã
Bi(2)Ã
Bi(2)Ã
Bi(2)Ã
/
O(12)
2.122(7)
2.275(7)
2.353(8)
2.534(7)
2.547(8)
2.666(7)
2.928(8)
2.129(7)
2.306(7)
2.312(7)
2.556(8)
2.581(7)
2.624(7)
2.847(8)
(g molꢀ1
)
/O(23)#1
Crystal system
Space group
Temperature (K)
triclinic
¯
monoclinic
P21/n (No. 14)
298
/O(13)
P/1 (No. 2)
/O(21)
293(2)
/N(1)
˚
Wavelength (A)
0.71069
7.9815(14)
9.651(4)
10.940(2)
73.95(2)
79.80(2)
89.42(2)
796.4(4)
2.962
0.71069
/O(11)
˚
a (A)
6.2137(12)
20.907(4)
8.3113(17)
/O(13)#2
˚
b (A)
/O(22)
˚
c (A)
/O(11)
a (8)
b (8)
g (8)
Volume (A )
Dcalc (g cmꢀ3
/O(21)
102.87(3)
/N(2)
/O(13)#3
3
˚
1052.6(4)
2.624
4
/O(23)
)
/O(11)#4
Z
4
22.095
Bond angles
O(12)ÃBi(1)Ã
O(12)ÃBi(1)Ã
O(23)#1Ã
O(12)ÃBi(1)Ã
O(23)#1ÃBi(1)Ã
O(13)ÃBi(1)Ã
O(12)ÃBi(1)Ã
O(23)#1Ã
O(13)ÃBi(1)Ã
O(21)ÃBi(1)Ã
O(12)ÃBi(1)Ã
O(23)#1Ã
O(13)ÃBi(1)Ã
O(21)ÃBi(1)Ã
N(1)ÃBi(1)Ã
O(12)ÃBi(1)Ã
O(23)#1ÃBi(1)Ã
O(13)ÃBi(1)Ã
O(21)ÃBi(1)Ã
N(1)ÃBi(1)Ã
O(11)ÃBi(1)Ã
O(22)ÃBi(2)Ã
O(22)ÃBi(2)Ã
O(11)ÃBi(2)Ã
O(22)ÃBi(2)Ã
O(11)ÃBi(2)Ã
Bi(2)ÃN(2)
O(22)ÃBi(2)Ã
O(11)ÃBi(2)Ã
O(21)ÃBi(2)Ã
N(2)ÃBi(2)Ã
O(22)ÃBi(2)Ã
O(11)ÃBi(2)Ã
O(21)ÃBi(2)Ã
N(2)ÃBi(2)Ã
O(13)#3ÃBi(2)Ã
O(22)ÃBi(2)Ã
O(11)ÃBi(2)Ã
O(21)ÃBi(2)Ã
N(2)ÃBi(2)Ã
O(13)#3ÃBi(2)Ã
O(23)ÃBi(2)ÃO(11)#4
Absorption
14.120
/
/
O(23)#1
85.5(3)
101.3(3)
73.2(3)
87.2(3)
100.2(2)
168.6(3)
73.9(3)
132.5(3)
69.7(3)
120.4(2)
107.4(3)
159.6(2)
117.8(2)
65.7(2)
67.4(2)
166.2(2)
83.7(2)
83.6(3)
86.4(2)
119.8(2)
80.9(2)
84.6(3)
100.2(3)
75.4(2)
73.8(3)
134.9(3)
70.4(3)
86.2(3)
97.6(2)
169.8(3)
119.3(3)
105.3(3)
157.9(2)
120.9(2)
67.2(2)
64.1(2)
154.4(2)
73.5(3)
87.0(3)
131.3(2)
83.9(2)
91.4(2)
coefficient (mmꢀ1
Reflections collected 3658
)
/
/O(13)
4463
/
Bi(1)Ã
O(21)
O(21)
/
O(13)
Independent
reflections
3658 [Rint
ꢄ/
0.0000] 1514 [Rint
ꢄ/0.0255]
/
/
/
/
Data/restraints/
parameters
3658/0/210
1514/0/141
/
/O(21)
/
/N(1)
R indices [I ꢀ
/
2s(I)] R1ꢄ
wR2ꢄ
R1ꢄ0.0578,
wR2ꢄ0.0857
Goodness-of-fit on F2 1.039
/
0.0358,
R1ꢄ
wR2
R1ꢄ
wR2ꢄ
/
0.0282,
0.0767
0.0293,
0.0775
/
Bi(1)ÃN(1)
/
/0.0796
ꢄ
/
/
/
/
N(1)
N(1)
O(11)
R indices (all data)
/
/
/
/
/
/
/
1.122
none
/
Bi(1)ÃO(11)
/
Extinction coefficient 0.00045(14)
/
/O(11)
/
/O(11)
/
/
O(11)
O(13)#2
O(13)#2
/
/
2.6. Structure of 2
/
/
/
/O(13)#2
/
/O(13)#2
Compound 2 was studied on a Bruker Smart IK
diffractometer equipped with a CCD area detector.
Refer to Table 1 for pertinent crystallographic data
regarding the complex. The data was corrected for
Lorentz and polarization effects. Absorption correction
was applied using the program SADABS (Sheldrick,
1997). Several reflection intensities were monitored
throughout the data collection and no decay of the
crystal was detected.
The structures were solved using direct methods with
the SHELXTL software package (Sheldrick, 2000). Heavy
atoms were located initially to set the correct phases for
the model. All other atoms were located by successive
Fourier maps and were refined using the full-matrix
least-squares method on F2. All non-hydrogen atoms
/
/
O(13)#2
/
/
O(13)#2
O(11)
O(21)
O(21)
N(2)
/
/
/
/
/
/
/
/
/
/
N(2)ÃO(21)
/
/
/
/
O(13)#3
O(13)#3
O(13)#3
/
/
/
/
/
/
O(13)#3
/
/
O(23)
O(23)
O(23)
/
/
/
/
/
/
O(23)
/
/
O(23)
/
/
O(11)#4
O(11)#4
O(11)#4
were refined anisotropically. Hydrogen atoms were
˚
ꢄ0.96 A) and
/
/
/
/
placed in calculated positions (dCÃH
/
/
/
O(11)#4
allowed to ride on the adjacent carbon atom. Refine-
ment of positional and anisotropic parameters led to
convergence.
/
/
O(11)#4
/
/
Symmetry transformations used to generate equivalent atoms: #1,
xꢀ1, y, z; #2, ꢀxꢀ1, ꢀyꢀ1, ꢀz; #3, xꢂ1, y, z; #4, ꢀx, ꢀyꢀ1, ꢀ
z.
In solving the structure only one asymmetric unit was
found in the molecule, despite experimental evidence
that suggests the presence of both bismuth and terbium
[8]. It appears that there is statistical occupational
/
/
/
/
/
/
/
/
/
/
/

252
R.E. Bachman et al. / Inorganica Chimica Acta 346 (2003) 249ꢁ255
/
disorder in the polymeric structure. As a consequence of
this observed disorder, they were constrained to be
equivalent and the structure was refined accordingly.
Analysis of the electron density at the metal site led to
the approximate ratio of bismuth to terbium of 7:3.
Other pertinent information about the compound in-
cluding significant bond distances and angles are
provided in Table 3.
[Bi(OCH2CH2)3N]n, (1) cleanly. Interestingly, the use
of freshly prepared Bi(OH)3 containing significant
quantities of water does not seem to adversely affect
the reaction. This observation would seem to suggest
that the multidentate nature of the ligand afford a
relatively high degree of hydrolytic stability. The
product can be conveniently, albeit slowly, isolated as
X-ray quality crystals by adding methanol and allowing
the solution to stand for two to 3 weeks. Once crystal-
lized, 1 is essentially insoluble in almost all organic
solvents. Given the apparent hydrolytic stability of 1, we
attempted to acquire its 1H NMR spectrum in D2O. The
spectrum consisted of two broad peaks centered at
approximately 2.8 and 4.0 ppm (for reference the
methylene signals of triethanolamine occur at ca. 2.7
and 3.7 ppm) [9]. The broad peaks and the small shifts
observed are consistent with expectations for a mixture
of oligomeric fragments arising from 1; however, it is
also possible that some or all of the observed signal is
due to hydrolysis products.
3. Results and discussion
The reaction of Bi(OH)3 with triethanolamine in basic
ethanolic media produces the targeted complex,
Table 3
˚
Key bond lengths (A) and angles (8) for 2
Bond lengths
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
Bi(1)Ã
O(12)Ã
O(12)Ã
O(31)Ã
O(31)Ã
/
O(21)
O(11)
O(2)
2.238(6)
2.265(6)
2.388(6)
2.485(6)
2.502(6)
2.528(7)
2.631(6)
2.697(7)
2.485(6)
2.485(6)
2.631(6)
2.631(6)
/
Thermogravametric analysis of 1 in either an argon or
oxygen atmosphere shows a net weight loss of approxi-
mately 35%, consistent with the formation of Bi2O3.
Bulk pyrolysis of 1 under oxygen produced gem-like
/
/
O(12)#1
O(31)
N(1)
/
/
/
O(31)#2
O(1)
particles with a goldenꢁyellow color. Powder diffraction
/
/
analysis of these particles indicated that they were
indeed Bi2O3. It is possible that the yellow color of
these materials arises from a small degree of nitrogen
incorporation. The partial inclusion of a slightly lighter
element for oxygen would help to explain the measured
weight loss, which is slightly larger than the theoretical
value of 34.4%. Additionally, the inclusion of nitrogen
dopants in other materials such as diamond is known to
give rise to a yellow color.
/
Tb(1)#3
Bi(1)#3
Tb(1)#2
Bi(1)#2
/
/
/
Bond angles
O(21)ÃBi(1)Ã
O(21)ÃBi(1)Ã
O(11)ÃBi(1)Ã
O(21)ÃBi(1)Ã
O(11)ÃBi(1)Ã
O(2)ÃBi(1)Ã
O(21)ÃBi(1)Ã
O(11)ÃBi(1)Ã
O(2)ÃBi(1)Ã
O(12)#1ÃBi(1)Ã
O(21)ÃBi(1)Ã
O(11)ÃBi(1)Ã
O(2)ÃBi(1)Ã
O(12)#1ÃBi(1)Ã
O(31)ÃBi(1)Ã
O(21)ÃBi(1)Ã
O(11)ÃBi(1)Ã
O(2)ÃBi(1)Ã
O(12)#1ÃBi(1)Ã
O(31)ÃBi(1)ÃO(31)#2
N(1)ÃBi(1)ÃO(31)#2
O(21)ÃBi(1)Ã
O(11)ÃBi(1)Ã
O(2)ÃBi(1)Ã
O(12)#1ÃBi(1)Ã
O(31)ÃBi(1)ÃO(1)
N(1)ÃBi(1)ÃO(1)
O(31)#2ÃBi(1)ÃO(1)
Bi(1)ÃO(31)Ã
Bi(1)ÃO(31)Ã
/
/
O(11)
84.1(2)
73.5(2)
77.5(2)
78.8(3)
144.1(2)
126.0(2)
135.2(2)
84.2(2)
144.1(2)
86.1(2)
70.0(2)
71.4(2)
133.7(2)
73.1(2)
65.2(2)
145.8(2)
73.7(2)
76.4(2)
33.4(2)
68.9(2)
124.0(2)
115.6(2)
140.8(2)
76.7(2)
75.0(2)
100.3(2)
145.7(2)
72.0(2)
111.1(2)
111.1(2)
/
/O(2)
/
/O(2)
/
/O(12)#1
/
/O(12)#1
As was mentioned earlier, 1 is isolated from the
reaction mixture as X-ray quality crystals allowing the
solid-state structure to be determined unambiguously.
/
/
O(12)#1
/
/O(31)
/
/O(31)
/
/
O(31)
¯
Compound 1 crystallizes in the P1 space group with two
/
/
/O(31)
complete formula units per asymmetric unit. Contrary
to expectations, the addition of an internal Lewis base
did not prevent oligomerization via bridging oxygen
atoms. The two independent bismuth atoms have similar
/
/N(1)
/
/N(1)
/
/
N(1)
/
/N(1)
/
/N(1)
coordination environments consisting of five short BiÃ
/
O
/
/O(31)#2
bonds and a BiÃ
/
N bond and a longer BiÃ
/
O contact
/
/O(31)#2
from an oxygen atom on an adjacent polymer chain
(Fig. 1).
/
/
O(31)#2
/
/O(31)#2
/
/
The BiÃ
/
O bonds, which range from 2.124(8) to
/
/
˚
2.667(7) A, compare well with those seen in other
bismuth alkoxides [10]. Not surprisingly, the shortest
of these bonds are the ones involving the non-bridging
oxygen atoms [O(12) and O(22)]. However, it is inter-
/
/O(1)
/
/O(1)
/
/
O(1)
/
/O(1)
/
/
esting to note that the longest of the BiÃ
/
O bonds
/
/
involves the non-bridging oxygen atom [O(11) and
O(23)], i.e. an oxygen atom belonging to the ligand
that chelates that metal atom (see Table 2 and Fig. 1).
These two oxygen atoms form significantly shorter
/
/
/
/Tb(1)#2
/
/Bi(1)#2

R.E. Bachman et al. / Inorganica Chimica Acta 346 (2003) 249ꢁ
/255
253
Fig. 1. Individual coordination environments of the metal center in 1 (top) and in 2 (bottom). Thermal ellipsoids are drawn at the 50% probability
level.
bonds with the ‘intermolecular’ metal atom they bridge
˚
to (2.667(7) versus 2.305(7) A for O(11)]. This pattern of
a ‘D’-shaped column structure (Fig. 2). Two of these
columns are in turn linked by a pair of BiÃO contacts,
one involving each bismuth atom. The result is a ‘ladder’
polymer with an almost cylindrical external shape in
which, the spiro bismantane polymers form the legs and
the and intercolumnar contacts are the rungs. These
/
one short and one long BiÃ/O bond for the bridging
oxygen atoms has been observed before in other
alkoxide species. Nitrogen bond lengths ranging from
˚
2.398(8) to 2.84(2) A have been reported for bismuth
complexes bearing donor nitrogen ligands [14]. The
intercolumnar contacts*
/
Bi(1)Ã
/
O(11)ꢄ2.847 and
/
˚
bismuthÃ/nitrogen bond distance of 1 compares well
Bi(2)Ã
/
O(13)ꢄ
/
2.927 A*
/are significantly longer than
with these observations. The nitrogen atoms on the two
independent units are arranged in an ‘anti’ type fashion
the intracolumnar BiÃ
/
O distances, but still significantly
˚
shorter than the sum of the van der Waals radii (3.67 A)
with a NÃ
/
BiÃ
/
BiÃ
/
N torsion angle of 1158.
[11] and only slightly longer than the longest BiÃ
/
O
˚
distances observed for a Bi2O3 (2.787 A) [12].
From a supramolecular perspective, the bridging
oxygen atoms construct an infinite chain of spiro-linked
1,3,2,4-dioxadibismetane rings with the bismuth atoms
forming the spiro linkage. These rings are almost planar
(sum of the interior angles are 357.8 and 356.78), with
only a small butterfly-like distortion and almost co-
planar with each other, with a dihedral angle of 58
between adjacent rings. The alternating orientation of
the organic portion of the triethanolamine ligand creates
Complex 2 crystallizes in the monoclinic space group
P21/n and is structurally similar to bismuth nitrilotria-
cetate complexes that have been reported previously
[13]. However, the complex bears the important distinc-
tion that it is heterobimetallic and contains both
bismuth and a lanthanide element in the structure.
There is occupational disorder in the lattice and the
two metal species present in the compound occupy

254
R.E. Bachman et al. / Inorganica Chimica Acta 346 (2003) 249ꢁ255
/
between the metal center of the complex and one of the
carbonyl oxygen in a neighboring nitriloacetate ligand.
The bond length for this interaction is relatively short
˚
(2.485(6) A), indicating that the dimers are strongly
associated in the solid state. It is noteworthy that this
structure is also similar to 1 in that the intracolumar
contacts are shorter than the intercolumar contacts.
The metal atom retains two waters of hydration to
complete its coordination sphere. Surprisingly, the bond
distances to the water molecules are shorter than the
bond distance to the covalently bound O31 in the
nitriloacetate ligand. This indicates that the water
molecules are strongly associated with the metal center.
The full structure of the complex is arranged so that
the four-membered bismuth oxygen ring system forms
the rungs of a ladder, while the dative association
between the metal and the neighboring acetate ligand
serve to assemble the legs of the structure. The water
molecules are located in the interior of the molecule
between the ‘rungs’ of the ladder in an alternating
orientation.
Fig. 2. View of the extended ladder polymer structure of 1 (A) and 2
(B). Thermal ellipsoids are drawn at 50% probability levels.
crystallographically identical and indistinguishable posi-
tions in the polymer network. Modeling the electron
density of the metal center during refinement of the
crystal structure led to the determination that the ratio
of bismuth to terbium in the structure was approxi-
mately 7:3. The metal stoichiometry suggested by the
crystallographic data is supported by both the elemental
and thermogravimetric data, and suggests that the ratio
of metal atoms is consistent throughout the sample.
The metal center of complex 2 is eight-coordinate.
Hypercoordinate complexes of nitriloacetate have been
reported for both bismuth [13] and the lanthanides [15].
Acknowledgements
We would like to thank the NSF and the Robert A.
Welch Foundation for support of this work.
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